Pension and Other Benefits (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1.1	$ 1.5	$ 2.2	$ 3.0
Interest cost	8.6	9.3	17.2	18.5
Expected return on plan assets	(8.5)	(8.5)	(17.0)	(17.0)
Amortization of prior service cost	0.0	0.0	0.0	0.0
Amortization of actuarial losses	2.7	2.7	5.5	5.5
Settlement and curtailment losses	0.0	0.5	0.0	0.5
NET PERIODIC BENEFIT COST	3.9	5.5	7.9	10.5
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.1	0.0	0.1	0.0
Interest cost	0.3	0.3	0.5	0.4
Expected return on plan assets	0.0	0.0	0.0	0.0
Amortization of prior service cost	(0.3)	(0.2)	(0.5)	(0.4)
Amortization of actuarial losses	0.1	0.0	0.1	0.0
Settlement and curtailment losses	0.0	0.0	0.0	0.0
NET PERIODIC BENEFIT COST	$ 0.2	$ 0.1	$ 0.2	$ 0.0